Hydrangea macrophylla plant named ‘HYMMAD I’

ABSTRACT

Hydrangea macrophylla,  ‘HYMMAD I’ has pure white mophead inflorescences that remain white in the presence and absence of aluminum. Inflorescences mature to a iridescent lime green. The habit is rounded with strong stems that hold the flowers upright. The lustrous, dark green leaves are highly mildew resistant.

Botanical classification: Hydrangea macrophylla.

Varietal denomination: ‘HYMMAD I’.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar ofHydrangea macrophylla, a member of the Hydrangeaceae family, hereinafterreferred to as ‘HYMMAD I’. This cultivar is grown primarily as anornamental for landscape use and for use as a potted plant, fresh cutand dried flowers. The cultivar originated from open-pollination ofHydrangea macrophylla ‘White Wave’ (non-patented), the pollen donorbeing unknown. It was selected at the University of Georgia, Athens, Ga.in 2002, from the progeny seedlings of this open pollination bycontinued evaluation for pure white mophead flowers unaffected by theabsence or presence of aluminum (Al), increased resistance to mildew,and improved leaf and flower characteristics.

‘HYMMAD I’ is distinguished from its female parent ‘White Wave’ by itspure white, mophead inflorescence that does not turn pink or blue in theabsence or presence, respectively, of Al. The inflorescence matures avirbrant lime green and maintains the color when utilized as driedflowers. ‘HYMMAD I’ has lustrous, more leathery, bullate, darker greenleaves than ‘White Wave’. ‘HYMMAD I’ had no mildew in late summer,whereas in side-by-side comparisons, ‘White Wave’ showed 25% infectionby mildew. The mophead inflorescence of ‘HYMMAD I’ is dense,domed-shaped, and the sepals completely cover the fertile flowerswhereas the lacecap inflorescence of ‘White Wave’ has a row of sterileflorets around the periphery and fertile flowers in the center.

‘HYMMAD I’ has better cold resistance than other white mopheads such as‘Regula’ (‘White Bouquet’) (unpatented), ‘Schwan’ (unpatented) or ‘SoeurThérèsa’ (unpatented) and the sterile florets do not have the pink orblue eye of ‘Mme Emile Mouillère’ (unpatented).

SUMMARY OF THE INVENTION

The following traits have been observed and represent thecharacteristics of the new cultivar. In combination thesecharacteristics distinguish ‘HYMMAD I’ from all other varieties incommerce known to the inventor:

-   -   1. Pure white flowers (sepals) that are not affected by the        presence or absence of Al and hold the color until maturation.    -   2. At maturation, sepals turn a vibrant lime green and dry to        this color.    -   3. Mophead inflorescences consist of numerous sepals that cover        the fertile flowers resulting in a dome of pure white.    -   4. Rounded habit and strong stems that hold the inflorescences        upright.    -   5. Lustrous, leathery, bullate, dark green leaves.    -   6. Mildew resistant leaves. Plants of this cultivar have shown        greater mildew resistance than all other white mophead varieties        of Hydrangea macrophylla known to the inventor.

‘HYMMAD I’ has been asexually propagated in Athens, Ga. since 2002. Thecharacteristics of the cultivar have been stable and reproducedtrue-to-type in successive vegetative generations.

BRIEF DESCRIPTION OF THE PHOTOGRAPHS

FIG. 1 shows a 2 year-old plant showing the lustrous dark green leavesand opening inflorescences.

FIG. 2 shows an opening inflorescence.

FIG. 3 shows a peak inflorescence showing pure white sepals with nocolored eyes.

FIG. 4 shows a mature, lime green inflorescence.

BOTANICAL DESCRIPTION OF THE PLANT

A detailed description of Hydrangea macrophylla ‘HYMMAD I’ follows.Colors are based on The Royal Horticultural Colour Chart (1995). Allmeasurements/characteristics were taken from 2 year-old plants growingin 11.8 liter containers under 50% shade at Athens, Ga., USDA Zone 7.Measurements of leaf/stems and floral characteristics are based on 10 to20 samples. The presence of Al means that the plant was treated withaluminum sulphate (42 g per 3.8 liters of water) applied as a soildrench when flower buds were visible.

-   Plant: The plant has a compact, upright, rounded growth habit, with    upright branches from the base, attaining a size of 28 cm high by 62    cm wide after 2 years.-   Stems: Current year stems are round, averaging 3.6 mm in diameter,    with no exfoliation and are Greyed-Yellow 161D, Greyed-Orange 165B    in color. The average internode length is 5.7 cm. Older stems are 6    mm in diameter, with no pubescence and flaky, and Greyed-Brown    N199B, Greyed-Brown N199C in color.-   Vegetative buds: The vegetative buds are in an opposite arrangement,    2 per node and flat on the stem. They are globose in shape, 5.5 mm    by 2.5 mm, and have 4 scales which are Greyed-Brown 199D in color.-   Flower buds: The flower buds are round in shape with no pubescence,    3.5 mm by 3.5 mm by 3 mm, and White 155B in color. They develop in    the early summer.-   Leaf: The leaves, in opposite arrangement, are ovate in shape with    acute base, acuminate apex and serrulate margin. The mature leaf is    9.3 cm long by 6.4 cm wide, very thick, leathery and very waxy. The    color of the emerging leaf is Yellow-Green 144A on the upper and    Yellow-Green 144B on the lower surfaces, maturing to Green 139A on    the upper surface and Green N138C on the lower. The venation is    pinnate, with Yellow-Green 146C veins.

The petioles average 2.3 cm long and 3 mm in diameter are grooved aboveand rounded below, with no pubescence, and are Yellow-Green 144A incolor.

-   Inflorescence: The bloom period is from mid May to the end of June,    with the mature, green inflorescence persisting into the fall. The    number of flowers in a mophead inflorescence varies widely. The    inflorescence averages 12.5 cm in diameter and 8 cm deep.

There are on average 8 inflorescences per plant, one per terminalbranch.

-   Sterile florets: There are typically 4 sepals, sometimes 3, roundish    in shape with acute apex, acute base and with a mostly entire margin    with an occasional serration. The texture is smooth with no    pubescence. The sepals average 16.6 mm long by 16.5 mm wide and the    floret is 38 mm by 38 mm. The upper and lower surfaces are white    (pure, The R.H.S. Colour Chart contains white with shadings of blue,    pink or green, but does not have a pure white) in absence and    presence of Al.

The peduncle has no pubescence and is Yellow-Green 144A in color.

The pedicel is finely pubescent, 21 mm in length by 1 mm wide and whitein color.

-   Fertile flowers: The 4 petals per flower are ovate in shape, with    acute apex, rounded base and an entire margin. They are 3 mm in    length by 1 mm wide, with a smooth texture and no pubsecence. Their    color is white.

There are 10 anthers, 1 mm long by 1 mm wide and white 155B in color.

The filament is 3.7 mm long by 0.5 mm wide and white in color.

The superior pistil is globose in shape, 2 mm long by 1 mm wide with nopubescence and white in color.

The stigma is oval, with no pubescence and white in color.

The style is tubular in shape, 1 mm long with no pubescence and white incolor.

No ovaries were apparent.

-   Fruit: The fruit is a capsule, oval in shape, 2 mm long by 1 mm    wide, Green 143B in color.-   Seed: The seeds are 0.5 mm long by 0.25 mm wide and Greyed-Orange    164C in color.

1. A new and distinct variety of Hydrangea macrophylla plantsubstantially as herein described and illustrated.